Upgrading from CGAL::Object to boost::variant

Code can be upgraded by using either boost::get or the boost::static_visitor<T>.

#include <CGAL/intersections.h>

template<typename R>
struct Intersection_visitor : public boost::static_visitor<> {
  void operator()(const Point_2& p) const 
  { // Point_2  
  }
  void operator()(const Segment_2& s) const 
  { // Segment_2 
  }
};

template <class R>
void foo(Segment_2<R> seg, Line_2<R> lin)
{
  CGAL::Object obj = intersection(seg1, seg2);
  if(const Point_2* foo = object_cast<Point_2>(&obj)) {
    // Point_2 
  } else if(const Segment_2* foo = object_cast<Segment_2>(&obj)) {
    // Segment_2 
  } else {
    // empty
  }

  // becomes
  auto result = intersection(seg, lin);
  if(result) {
    if(const Point_2* foo = boost::get<Point_2>(&*obj)) {
      // Point_2 
    } else if(const Segment_2* foo = boost::get<Segment_2>(&*obj)) {
      // Segment_2 
    }
  } else {
    // empty
  }

  // or with boost::static_visitor<T>
  if(result) { boost::apply_visitor(Intersection_visitor(), *result); } 
  else { // empty  
  }
}